1. Field of the Invention
The present invention relates to a beamforming apparatus for an ultrasonic imaging system and, in particular, to a beamforming apparatus that is capable of generating appropriately delayed samples in a broad frequency spectrum by implementing fractional delay (FD) filter using post-filtering which requires lower hardware complexity than the conventional interpolation filter or IQ phase rotator.
2. Description of the Related Art
Conventional delay-sum beamformers employ four-fold interpolation filters for effectively increasing data transmission rate (over 16 f0 for fine delay control). Finite impulse response (FIR) filters are ideal for this effect since FIR filters generate delayed samples with no phase error but with some amplitude errors. However, the interpolation filter requires a plurality of multipliers. In the meantime, a phase rotation beamformer requires two FIR low pass filters (FIR LPFs) for In-phase and Quadrature (IQ) demodulation and 4 real number multipliers for phase rotation of IQ signals per channel.
However, such types of beamformers have been developed for creating high quality video image, thereby being not appropriate for portable ultrasonic scanners that should be designed in consideration of power consumption, manufacturing cost, and size.